This invention pertains to apparatus and methods for sorting plastic bottles for recycling.
The marketability of presorted plastic bottles is significantly greater than the marketability of unsorted plastic bottles. Thus, it is advantageous to sort plastic bottles for recycling into marketable categories. Sortation of plastic beverage and household containers has been performed manually, which is a labor intensive, expensive, and often inaccurate process. As recycling efforts in communities increase, so does the need for a faster and more efficient recycling sorting method.
Various arrangements have been proposed for accomplishing these tasks. Reed, U.S. Pat. No. 4,919,534, sorts returned glass and PET bottles by testing the material with polarized and colorized light. Alternately flashing red and green polarized light is optically detected as the light passes through the bottle. The rotation of the polarized light differentiates between glass and PET.
Plester, U.S. Pat. No. 4,858,768, removes plastic bottles which have been contaminated previous to their arrival at the sorting center. Warm water is injected into the plastic bottle, agitated, and various residue analyzers determine the characteristics of the residue. For example, electromagnetic radiation, light scattering, polarized light rotation, and X-ray fluorescence may be used to examine the residue.
Thompson et. al, U.S. Pat. No. 4,248,389, discloses a detector which sorts recycled bottles by scanning the Universal Product Code, using that code to classify the bottle, and sorting the bottle into the appropriate bin for later reclamation.
Schneider, U.S. Pat. No. 3,358,552, discloses sorting bottles by optically determining the placement of a label, the color of the bottle, and the pattern engraved in the glass. The outlets of these sensors are fed into a logic circuit, which then determines the commercial affiliation of the bottle by determining the combination of the triggered detectors.
Kelly, U.S. Pat. No. 4,848,590, discloses sorting different types of scrap metal on the basis of their X-ray fluorescence. Depending on the type of metal detected, the metal is directed to various storage areas.
Japanese Patent No. 56145339 generally discloses detecting chlorine in a vinyl chloride resin to determine the degree of aging of the resin.
Lundell, U.S. Pat. No. 5,024,335, discloses a mechanical sorter for removing large plastic containers and aluminum cans from other refuse. A variety of refuse is transported below rotating brushes. Those containers which are too large to fit under the brushes are lifted off the conveyors and over the top of the brushes. After the containers pass over the top of the brushes, they are diverted to a separate conveyor for later removal.
Despite all of this effort toward the development of recycling methods and apparatus, there are needs for further improvement.